On 01/12/2021 16:39, Arunpravin wrote:
On contiguous allocation, we round up the size
to the *next* power of 2, implement a function
to free the unused pages after the newly allocate block.
v2(Matthew Auld):
- replace function name 'drm_buddy_free_unused_pages' with
drm_buddy_block_trim
- replace input argument name 'actual_size' with 'new_size'
- add more validation checks for input arguments
- add overlaps check to avoid needless searching and splitting
- merged the below patch to see the feature in action
- add free unused pages support to i915 driver
- lock drm_buddy_block_trim() function as it calls mark_free/mark_split
are all globally visible
v3:
- remove drm_buddy_block_trim() error handling and
print a warn message if it fails
Signed-off-by: Arunpravin <Arunpravin.PaneerSelvam@xxxxxxx>
---
drivers/gpu/drm/drm_buddy.c | 72 ++++++++++++++++++-
drivers/gpu/drm/i915/i915_ttm_buddy_manager.c | 10 +++
include/drm/drm_buddy.h | 4 ++
3 files changed, 83 insertions(+), 3 deletions(-)
diff --git a/drivers/gpu/drm/drm_buddy.c b/drivers/gpu/drm/drm_buddy.c
index eddc1eeda02e..707efc82216d 100644
--- a/drivers/gpu/drm/drm_buddy.c
+++ b/drivers/gpu/drm/drm_buddy.c
@@ -434,7 +434,8 @@ alloc_from_freelist(struct drm_buddy_mm *mm,
static int __alloc_range(struct drm_buddy_mm *mm,
struct list_head *dfs,
u64 start, u64 size,
- struct list_head *blocks)
+ struct list_head *blocks,
+ bool trim_path)
{
struct drm_buddy_block *block;
struct drm_buddy_block *buddy;
@@ -480,8 +481,20 @@ static int __alloc_range(struct drm_buddy_mm *mm,
if (!drm_buddy_block_is_split(block)) {
err = split_block(mm, block);
- if (unlikely(err))
+ if (unlikely(err)) {
+ if (trim_path)
+ /*
+ * Here in case of trim, we return and dont goto
+ * split failure path as it removes from the
+ * original list and potentially also freeing
+ * the block. so we could leave as it is,
+ * worse case we get some internal fragmentation
+ * and leave the decision to the user
+ */
+ return err;
Hmm, ideally we don't want to leave around blocks where both buddies are
free without then also merging them back(not sure if that trips some
BUG_ON). Also IIUC, if we hit this failure path, depending on where the
split_block() fails we might be allocating something less than new_size?
Also if it's the first split_block() that fails then the user just gets
an empty list?
Could we perhaps just turn this node into a temporary root node to
prevent recursively freeing itself, but still retain the
un-splitting/freeing of the other nodes i.e something like:
list_del(&block->link);
mark_free(mm, block);
mm->avail += ...;
/* Prevent recursively freeing this node */
parent = block->parent;
block->parent = NULL;
list_add(&block->tmp_link, &dfs);
ret = _alloc_range(mm, &dfs, new_start, new_size, blocks);
if (ret) {
mem->avail -= ...;
mark_allocated(block);
list_add(&block->link, blocks);
}
block->parent = parent;
return ret;
That way we can also drop the special trim_path handling. Thoughts?
+
goto err_undo;
+ }
}
list_add(&block->right->tmp_link, dfs);
@@ -535,8 +548,61 @@ static int __drm_buddy_alloc_range(struct drm_buddy_mm *mm,
for (i = 0; i < mm->n_roots; ++i)
list_add_tail(&mm->roots[i]->tmp_link, &dfs);
- return __alloc_range(mm, &dfs, start, size, blocks);
+ return __alloc_range(mm, &dfs, start, size, blocks, 0);
+}
+
+/**
+ * drm_buddy_block_trim - free unused pages
+ *
+ * @mm: DRM buddy manager
+ * @new_size: original size requested
+ * @blocks: output list head to add allocated blocks
+ *
+ * For contiguous allocation, we round up the size to the nearest
+ * power of two value, drivers consume *actual* size, so remaining
+ * portions are unused and it can be freed.
+ *
+ * Returns:
+ * 0 on success, error code on failure.
+ */
+int drm_buddy_block_trim(struct drm_buddy_mm *mm,
+ u64 new_size,
+ struct list_head *blocks)
+{
+ struct drm_buddy_block *block;
+ u64 new_start;
+ LIST_HEAD(dfs);
+
+ if (!list_is_singular(blocks))
+ return -EINVAL;
+
+ block = list_first_entry(blocks,
+ struct drm_buddy_block,
+ link);
+
+ if (!drm_buddy_block_is_allocated(block))
+ return -EINVAL;
+
+ if (new_size > drm_buddy_block_size(mm, block))
+ return -EINVAL;
+
+ if (!new_size && !IS_ALIGNED(new_size, mm->chunk_size))
+ return -EINVAL;
+
+ if (new_size == drm_buddy_block_size(mm, block))
+ return 0;
+
+ list_del(&block->link);
+
+ new_start = drm_buddy_block_offset(block);
+
+ mark_free(mm, block);
+
+ list_add(&block->tmp_link, &dfs);
+
+ return __alloc_range(mm, &dfs, new_start, new_size, blocks, 1);
}
+EXPORT_SYMBOL(drm_buddy_block_trim);
/**
* drm_buddy_alloc - allocate power-of-two blocks
diff --git a/drivers/gpu/drm/i915/i915_ttm_buddy_manager.c b/drivers/gpu/drm/i915/i915_ttm_buddy_manager.c
index 7c58efb60dba..c5831c27fe82 100644
--- a/drivers/gpu/drm/i915/i915_ttm_buddy_manager.c
+++ b/drivers/gpu/drm/i915/i915_ttm_buddy_manager.c
@@ -97,6 +97,16 @@ static int i915_ttm_buddy_man_alloc(struct ttm_resource_manager *man,
if (unlikely(err))
goto err_free_blocks;
+ if (place->flags & TTM_PL_FLAG_CONTIGUOUS) {
+ mutex_lock(&bman->lock);
+ err = drm_buddy_block_trim(mm,
+ (u64)n_pages << PAGE_SHIFT,
+ &bman_res->blocks);
+ mutex_unlock(&bman->lock);
+ pr_warn("drm_buddy_block_trim failed returing %d for ttm_buffer_object(%p)\n",
+ err, bo);
IIUC this prints a warning even for success? Anyway, I think we can drop
the pr_warn, since normal user can't really do much here?
+ }
+
*res = &bman_res->base;
return 0;
diff --git a/include/drm/drm_buddy.h b/include/drm/drm_buddy.h
index 316ac0d25f08..90906d9dbbf0 100644
--- a/include/drm/drm_buddy.h
+++ b/include/drm/drm_buddy.h
@@ -146,6 +146,10 @@ int drm_buddy_alloc(struct drm_buddy_mm *mm,
struct list_head *blocks,
unsigned long flags);
+int drm_buddy_block_trim(struct drm_buddy_mm *mm,
+ u64 new_size,
+ struct list_head *blocks);
+
void drm_buddy_free(struct drm_buddy_mm *mm, struct drm_buddy_block *block);
void drm_buddy_free_list(struct drm_buddy_mm *mm, struct list_head *objects);
